The present invention relates generally to chucks for use with drills or with electric or pneumatic power drivers. More particularly, the present invention relates to a chuck of the keyless type which may be tightened or loosened by hand or by actuation of the driver motor.
Both hand and electric or pneumatic tool drivers are well-known. Although twist drills are the most common tools used with such drivers, the tools may also comprise screwdrivers, nut drivers, burrs, mounted grinding stones, and other cutting or abrading tools. Since the tools may have shanks of varying diameter or may have a polygonal cross-section, the device is usually provided with a chuck that is adjustable over a relatively wide range. The chuck may be attached to the driver by a threaded or tapered bore.
A wide variety of chucks have been developed in the art. In one form of chuck, three jaws spaced circumferentially approximately 120 degrees apart from each other are constrained by angularly disposed passageways in a body attached to the driveshaft. The chuck is configured so that rotation of the body in one direction with respect to a constrained nut forces the jaws into or away from a gripping relationship with a tool shank. Such a chuck may be keyless if it can be tightened or loosened by manual rotation. Examples of such chucks are disclosed in U.S. Pat. Nos. 5,011,167, 5,125,673, 5,193,824, and 5,816,584, each of which is commonly assigned to the present assignee and the entire disclosures of which are incorporated by reference herein. Various configurations of keyless chucks are known in the art and are desirable for a variety of applications.
FIG. 3A illustrates, in cross-section, a chuck jaw construction in which each of three jaws 200 includes a back surface 202 and an opposing tool engaging surface formed by a ridge 204 disposed generally parallel to the chuck axis. Two generally planar side surfaces 206 extend from ridge 204 to the back surface. The side surfaces 206 on each jaw 200 define an angle of approximately 120 degrees extending through the jaw. Thus, each side surface on a jaw 200 is generally parallel to a side surface of an adjacent jaw. When the chuck is moved to its fully closed position as shown in FIG. 3A, the jaw side surfaces abut each other. FIG. 3B is a side view of a prior art jaw 200 having threads 234 and a tool engaging jaw face 225. FIG. 3C is another prior art chuck jaw having threads 234, a tool engaging jaw face 225, and serrations 227 in face 225. Serrated jaws typically have a decreased surface area to grip the tool and, therefore, apply a greater force per square inch than a non-serrated jaw face, all other factors being equal.
Other tool engaging surfaces are known. For example, the tool engaging surface may be formed by an inner ridge parallel to the chuck axis and two outer ridges parallel to the inner ridge. A pair of respective troughs sit between the inner ridge and the outer ridges so that the jaw""s cross-section is in the shape of a xe2x80x9cW.xe2x80x9d Generally, side surfaces that extend from the outer ridges to the jaw""s back surface define a 120 degree angle between them through the jaw so that each side surface is parallel to the side surface of its adjacent jaw.
It is also known to grind the surfaces of chuck jaws in an assembled chuck to ensure that a tool shank gripped by the chuck jaws will be centered on the chuck axis. A grinding burr may be centered on the chuck axis to grind each jaw simultaneously as the assembled chuck moves axially with respect to the grinding burr.
Various configurations of keyless chucks and chuck jaws are known in the art and are desirable in a variety of applications.
The present invention recognizes and addresses disadvantages of prior art construction and methods.
Accordingly, it is an object of the present invention to provide an improved chuck jaw for use with a powered driver.
It is a more particular object of the present invention to provide an improved method of imparting a grind into a tool engaging jaw face in an assembled chuck.
It is a further object of the present invention to provide a method of imparting a helical grind to the tool engaging jaw faces of an assembled chuck in essentially a one-step process.
These and other objects are achieved by a chuck for use with a manual or powered driver having a rotatable drive shaft. The chuck includes a generally cylindrical body having a nose section and a tail section. The tail section is configured to rotate with the drive shaft and the nose section has an axial bore formed therein. A plurality of jaws are movably disposed with respect to the body toward and away from the axial bore. Each jaw includes a back surface and a tool engaging surface opposite the back surface. The tool engaging surfaces are disposed facing generally parallel to the axis of the axial bore and a plurality of grinds are defined across each tool engaging surface to form a helical pattern on the chuck jaw when the tool engaging surfaces are disposed at a predetermined position with respect to the axis of the axial bore.